Pen thickness on Markup iOS11 iPad Pro

I want to keep this conversation alive so I re-upped the comment. After fiddling with the Markup tools on my iPad Pro for some time, here's what I found. The Markup app works very differently on a .jpg or a .pdf in either case, you can't adjust line thickness or "texture". You can only change color, and no matter that I always use red, each time I use the app again, it defaults to black. I use this app a lot to markup technical drawings. I also have PDF Expert, Skitch, Paper, Sketchbook, etc. But, because of iOS's barely functional file management system, using other apps is a matter of chasing my files down a labyrinth that changes with each app. I really think I should be able to perform relatively simple tasks with the native Markup app (or Tool as Apple refers to it).

Here's one really frustrating aspect that I will identify here so that other frustrated users can say "amen" to and not start to think they are alone in their frustration... ready? The pen tool works completely differently on a .jpg than on a .pdf. On a .jpg, you get a thick line that is pressure sensitive and too thick for any use. On a .pdf you get a thin non-pressure sensitive line that is sometimes too thin. I can't figure out why it's too thin on some files and about right on others. So, there you have it...you are not alone.